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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 43856
Experience:  16 years experience
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Have a 1999 Windstar 3.8L had 171 173 lean both banks no

Customer Question

have a 1999 Windstar 3.8L had 171 173 lean both banks no other codes. found MAF at 150.2 Hertz. checked for vacuum leaks found non, I Replaced the MAF and reset KAM, test drove Baro went to 158hz after about 30 miles of driving, thought the problem was cured, got a call now there are codes P0172 p0175 for rich both banks, data logged found baro at 160hz now and short term and long term going - on both banks, I think I got the wrong MAF, what is your advise
Submitted: 7 months ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 7 months ago.

Welcome, I'm Chris (aka Moose). Experts aren't employees / agents of Just Answer. We are independent service providers using the Site to sell their Expert knowledge to Customers. I strive to provide EXCELLENT 5 STAR service, let me know what's needed from me so your pleased.

  1. What is your zip code or height above sea level?
  2. Have you done any of the repairs for these quite common lean/rich codes on this model?
  3. What are the short term trims at hot idle on both banks?
Customer: replied 7 months ago.
sea level , Seattle area
I am a Senior Master diesel and gas Ford Tech, have done lots of these, but always used Motorcraft parts, on this one I used aftermarket and I am thinking the aftermarket MAF is the problem, ST on both banks was 7.80 on both banks with old MAF, and once the new maf got to 158hz it was at around -2 on both banks ST and LT so I thought it was fix, I released the car, the guy calls me 4 day later says the lite came back on, scanned found rich on both banks, i'm thinking the MAF is for a 3.0l
Customer: replied 7 months ago.
the MAF is showing more air than it should, voltage is right .95v at idle just the calibration is different
Customer: replied 7 months ago.
I know its a tough one, I have a name brand MAF on the way for it, just wanted to verify I was on the right track
Expert:  Chris (aka- Moose) replied 7 months ago.

Seattle is at sea level so the BARO reading should be 158.9 HZ. Your at 160 that is pretty darn close. So I would have t say the MAF is reading right.

You mentioned smoke testing the intake for leaks. Ford does not recommend that procedure because it rarely finds leaks. If one cylinder is at TDC exhaust there is valve overlap where both valves are barely open resulting in the smoke going into the intake and into that one cylinder and out the exhaust, unable to build pressure and come out where leaks would be.

Below is a link to a very common TSB for addressing lean codes on this model.

You mentioned the wrong MAF, they are different 3.0-3.8 but the barometric pressure reading should still come out the same on both.

What are the fuel trims at hot idle now since the codes have gone from lean to rich?

Thanks for asking your question and letting me try to help you.

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Expert:  Chris (aka- Moose) replied 7 months ago.

Hello again Chris here,

1) When customers come to Just Answer the website and the experts want them to have a great 5 star experience.

2) We also want them to be so pleased that they come back for future needs.

3) I have the feeling you were not pleased with my help and or need me to help more. If so please do reply.

4) I have an option to upload diagrams, repair guides, find a repair facility, or call you if that would help.

Thanks Chris